STP435

    Hard-Rolled Aluminum Alloys

    Published: Jan 1968


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    Abstract

    In 1955 exposure tests were started with the following architectural aluminum alloys in hard-rolled condition: high-purity aluminum, commercial purity aluminum (with and without 0.14 per cent copper), AlMn1.2 (with and without 0.14 per cent copper), AlMg0.65, AlMg2.5, Alclad (with core of AlMn1.2 and cladding of AlZn1). Panels of the alloys were exposed on five sites in Sweden with rural, marine, urbanmarine, and industrial atmospheres.

    After one-, three-, six-, and ten-years' exposure, specimens were taken in and examined with respect to pitting, layer corrosion, and change in mechanical properties.

    From the results it may be concluded that the hard-rolled AlMg alloys are well suited for architectural purposes. There is no risk of blistering, and the pitting corrosion resistance is as good as for unalloyed aluminum. With hard-rolled, unalloyed aluminum of commercial purity and AlMn1.2, both without copper, the risk of blistering cannot be disregarded, at least not in a marine atmosphere. Here layer corrosion blisters were formed on the alloys mentioned in most cases already during the first year of exposure. After the initial period, however, they generally developed very slowly. One way to overcome the susceptibility to blistering apparently is to add about 0.1 to 0.2 per cent copper. Another remedy might be to use alloys in half-hard condition, which is common practice. The alclad surface developed a rather rough appearance.

    It may be concluded that all the alloys tested will last for several decades in outdoor use, as far as the mechanical properties are concerned. Corrosion, however, may affect the appearance by pitting, blistering, roughening, and discoloration. Often, however, such “aging phenomena” may be regarded as an attractive patina.

    Keywords:

    aluminum, aluminum alloys, atmospheric corrosion tests, pitting, blistering


    Author Information:

    Mattsson, E
    Teknisk licentiat, docent, and chemical engineer, AB Svenska Metallverken, Finspong,

    Lindgren, S
    Teknisk licentiat, docent, and chemical engineer, AB Svenska Metallverken, Finspong,


    Paper ID: STP34091S

    Committee/Subcommittee: G01.04

    DOI: 10.1520/STP34091S


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